Lens driving mechanism and image capture apparatus

ABSTRACT

This prevents biting and miniaturizes an entire mechanism. There is provided a lens driver including: a driver having a frame that holds a lens and a bearing for receiving a guiding axis to move the lens in an optical axis direction, a lead screw in which a screw to which a nut is screwed is formed, and a stepping motor for rotating the lead screw; an arm extended from the frame, in such a way a tip being next to the nut, and moving the frame by movement of the nut; a spring for pushing an arm tip towards the nut; and an idle rotation section placed on only side where the arm is placed for the nut at a lead screw end of the driver, and has an axis diameter disabling the nut to be screwed. Also there is provided an image capture apparatus having the lens driver.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 10/846,636, filed on May 17, 2004 now U.S. Pat. No. 6,950,244 andbased upon and claims the benefit of priority to Japanese PatentApplication No. 2003-140027, filed on May 19, 2003, the entire contentseach of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens driving mechanism and an imagecapture apparatus that move a lens, which carries out a focusingoperation and the like, in an optical axis direction, and morespecifically a lens driving mechanism and an image capture apparatusthat have a clearance in the driving mechanism if an error occurs in amovement control of a lens.

2. Description of Related Art

In recent years, improvement of portability and advancement ofconvenience are demanded for the image capture apparatuses, such as adigital still camera, a digital video camera and the like. Furthermore,reduction of the total apparatus size and sizes of an optical systembarrel and lens used in the image capture apparatus are advanced.Further, demands for higher picture quality and more pixels are alsostrong. Accordingly, the miniaturization of the optical system barrel isdesirable by reducing the size of the driving mechanism even if the lensthat is a constituting element of the optical system is made larger.

Further, with regard to a so-called collapsible lens used in the imagecapture apparatus, such as a digital still camera, a digital videocamera and the like, reduction in size and thickness are desirable inview of portability convenience as mentioned above. Specifically, thereis a trend such that modern digital still camera having higherportability and convenience is more favored, since it can be put in apocket of a shirt or a pocket of jeans and the like. Accordingly, forthe optical system barrel, reduction in its thickness is highlydesirable.

Such a collapsible lens and collapsible barrel are disclosed in JapanesePatent Application Publication JP 2002-296480, and the lens drivingmechanism is disclosed in Japanese Patent Application Publication JP2002-287002 and the like. In these techniques, a lead screw, a guidingaxis, a nut and forcing element are used to constitute the lens drivingmechanism. The movement of the nut through the rotation of the leadscrew causes a lens holding frame to move in a direction of an opticalaxis.

[Patent Document 1]

-   -   Japanese Patent Application Publication JP 2002-296480        [Patent Document 2]    -   Japanese Patent Application Publication JP 2002-287002

SUMMARY OF THE INVENTION

However, in such conventional techniques, if a control error or the likeoccurs and cause parts that is to be driven (a lens frame) to reach anend of driving limit, the nut tries to move beyond a movement limit. Inconsequence, biting of a screw thread of the nut may occur, and become acause of parts damage and troubles in cameras.

In the technique disclosed in Japanese Patent Application Publication JP2002-287002 an idle rotation section for idly rotating nuts are placedat a base section and a tip section of the lead screw, as a unit forpreventing such biting of the screw thread of the nut.

However, if such an idle rotation section is provided, it is verydifficult to shorten the lead screw. Further, since the forcing elementis placed on the base side and tip side of the guiding axis, it isdifficult to shorten the guiding axis and a tip cover of the guidingaxis. In consequence, there is drawback such that those factors maybecome hindrance to further reduction in size of the lens barrel, whichis configured as a unit, and reduction in thickness of storage space forthe collapsible barrel.

The present invention is made in view of above-mentioned background.According to an embodiment of the present invention, there is provided alens driving mechanism including: a lens holder that holds a lens andhas a bearing section for receiving a axis for guiding the lens to movein an optical axis direction; driving means that has an output axis, inwhich a screw section to which a nut is screwed is formed, and a drivingsource for rotating the output axis; an arm that is provided byextending the lens holder, in such a way that a tip being located nextto the nut of the driving means, and moves the lens holder with movementof the nut; forcing means for forcing the tip of the arm in a directionto the nut; and an idle rotation section that is placed on one side, onwhich the arm is placed for the nut, at an end of the output axis of thedriving means, and has an axis diameter which disables the nut to bescrewed. Further, there is provided an image capture apparatus havingthis lens driver.

In present invention having the above-mentioned configuration, the idlerotation section is provided on only one end of the output axis to whichthe nut is screwed. Accordingly, as compared with a case in which theidle rotation sections are placed both ends of the output axis, thepresent invention makes it possible to shorten the length of the outputaxis.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description ofthe presently preferred exemplary embodiment of the invention taken inconjunction with the accompanying drawing, in which:

FIGS. 1A, 1B and 1C are perspective views explaining a situation of acollapsible lens;

FIGS. 2A, 2B and 2C are sectional views of the collapsible lens;

FIG. 3 is an exploded perspective view of the collapsible lens;

FIG. 4 is a partially sectional view explaining a first embodiment;

FIG. 5 is a partially sectional view explaining a second embodiment;

FIG. 6 is a partially sectional view explaining a third embodiment; and

FIG. 7 is a partially sectional view explaining a fourth embodiment.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below withreference to the attached drawings. At first, a lens barrel (acollapsible lens) of an image capture apparatus, which may be employedin a lens driving mechanism according to an embodiment of the presentinvention is applied, is explained. FIGS. 1A, 1B and 1C are perspectiveviews for explaining modes of the collapsible lens. FIG. 1A shows a lensstorage space mode when it is not used, namely, a collapsed mode, FIG.1B shows a WIDE mode, and FIG. 1C shows a TELE mode. Further, FIGS. 2A,2B and 2C are sectional views of the collapsible lens. FIG. 2A shows thesinking mode, FIG. 2B shows the WIDE mode, and FIG. 2C shows the TELEmode. Further, FIG. 3 is an exploded perspective view of the collapsiblelens.

A collapsible lens 1 has, in an optical sense, a three-groupconfiguration. A first group and a second group carry out a zoomingoperation by driving them in an optical axis direction along apredetermined cam curve, and a third group carries out a focusingoperation by being slightly displaced in the optical axis direction. Inother words, the collapsible lens 1 has a configuration such that thedisplacements of the first and second groups vary a focal distance andthe displacement of the third group performs proper focusing.

A first group frame 2 includes: three (a plurality of) cam pins 2 a tobe engaged with cam grooves 4 b of a cam ring 4; a plurality of lensspaces 2 b for inserting and fixing a plurality of lenses constitutingthe first group; and a barrier mechanism section 2 c for protecting afront lens in the sinking mode when it is stored. For example, the firstgroup frame is formed with polycarbonate resin (black) including glassfiber, and has strength, a light shielding property and is suited formass-production.

A second group frame 3 includes: three (a plurality of) cam pins 3 a tobe engaged with cam grooves 4 c of the cam ring 4; and a plurality oflens spaces 3 b for inserting and fixing a plurality of lensesconstituting the second group. For example, the second group frame isformed with polycarbonate resin (black) including glass fiber, and hasstrength, a light shielding property and is suited for mass-production.Alternatively, there may be a case that an iris shutter mechanism isfurther provided.

The cam ring 4 includes: a gear section 4 a for rotationally driving thecam ring 4 with an inner diameter of a fixed barrel 6 by being driven bya gear unit 10; three (a plurality of) cam grooves 4 b with which thecam pins 2 a of the first group frame 2 are engaged; three (a pluralityof) cam grooves 4 c with which the cam pins 3 a of the second groupframe 3 are engaged; and three (a plurality of) cam pins 4 d that is tobe engaged with cam grooves 6 a of the fixed ring 6. For example, thecam ring 4 is formed with polycarbonate resin (black) including glassfiber, and has strength, a light shielding property and is suited formass production.

The cam grooves 4 b and 4 c move the first and second groups in theoptical axis direction along a predetermined curve and carry put azooming operation. A linear-movement guiding ring 5 is a member that ismoved in the optical axis direction with the inner diameter of the fixedring 6 integrally with the cam ring 4, and it includes: a guiding groove5 a for guiding the first group frame 2 in the optical axis direction;and a guiding groove 5 b for guiding the second group frame 3 in theoptical axis direction. For example, the cam grooves 4 b and 4 c areformed with polycarbonate resin (black) including glass fiber, and hasstrength, a light shielding property and is suited for mass-production.

The fixed ring 6 is the member fixed to a rear barrel 8, and has thethree (the plurality of) cam grooves 6 a with which the cam pins 4 d ofthe cam ring 4 are engaged. For example, the fixed ring 6 is formed withpolycarbonate resin (black) including glass fiber, and has strength, alight shielding property and is suited for mass-production.

A third group frame 7 includes a lens space 7 a for inserting and fixingthe lenses constituting the third group. For example, the third groupframe 7 is formed with polycarbonate resin (black) including glassfiber, and has strength, a light shielding property and is suited formass-production. The third group frame 7 is movably held in the opticalaxis direction with respect to the rear barrel 8. A third group frame 7can be slightly displaced in the optical axis direction by a drivingsource such as a stepping motor 15 or the like. This third group frame 7corresponds to the lens holder of a lens driving mechanism according tothe present embodiment.

The rear barrel 8 includes: a recessed section for inserting,positioning and fixing an optical filter 11 such as an optical low-passcut filter, an infrared cut filter or the like; and a recessed sectionfor inserting a sealing rubber 12 to keep dust and the like out of thebarrel and to elastically apply force to the optical filter 11. Forexample, the rear barrel 8 is formed with polycarbonate resin (black)including glass fiber, and has strength, a light shielding property andis suited for mass-production. A solid imaging device 13, such as CCD,MOS or the like, is positioned and fixed to the rear barrel 8 at a highprecision.

The gear unit 10 drives the cam ring 4 through the gear sections 4 a. Agear ratio is determined such that sufficient driving force may beobtained in the mode ranges of “Collapsed →WIDE →TELE” and “TELE →WIDE→Collapsed”. The gear unit 10 drives the cam ring 4 so as to carry outthe zooming operation of the collapsible lens.

The stepping motor 15 includes: a lead screw 15 a for displacing thethird group frame 7 in the optical axis direction; and an attachment 15d to be positioned and fixed to the rear barrel 8. This stepping motor15 corresponds to the driving source of the lens driving mechanism, andthe lead screw 15 a corresponds to the output axis according to thepresent embodiment.

The operation of the lens will be described below. In the operationbetween the collapsed mode and the optical WIDE mode, the cam ring 4 isdriven by applying driving force to the gear section 4 a from the gearunit 10. Next, while the cam pin 4 d is rotated along the cam groove 6 aof the fixed ring 6, the cam ring 4 is moved towards a side of an objectto be imaged in the optical axis direction. At this time, thelinear-movement guiding ring 5 is moved integrally with the cam ring 4(refer to an arrow A of FIGS. 2A, 2B and 2C).

At this time, in the first group frame 2, the cam pins 2 a are moved ona predetermined curve along the cam groove 4 b and the guiding groove 5a (refer to an arrow B of FIGS. 2A, 2B and 2C). At this time, in thesecond group frame 3, the cam pins 3 a are moved on a predeterminedcurve along the cam groove 4 c and the guiding groove 5 b (refer to anarrow C of FIGS. 2A, 2B and 2C). As mentioned above, the first andsecond groups are moved to the predetermined positions and opticallylocated at the WIDE positions.

Further in the operation between the optical WIDE mode and the opticalTELE mode, the cam ring 4 is driven by applying driving force to thegear section 4 a from the gear unit 10. In this operation range, the camgroove 6 a is formed such that the cam ring 4 is not driven in theoptical axis direction. Further, the linear-movement guiding ring 5 isnot moved in the optical axis direction (refer to an arrow D of FIGS.2A, 2B and 2C).

At this time, in the first group frame 2, the cam pins 2 a are movedthrough the predetermined curve along the cam groove 4 b and the guidinggroove 5 a (refer to n arrow E of FIGS. 2A, 2B and 2C). At this time, inthe second group frame 3, the cam pins 3 a are moved through thepredetermined curve along the cam groove 4 c and the guiding groove 5 b(refer to an arrow F of FIGS. 2A, 2B and 2C). As mentioned above, thefirst and second groups are moved along the predetermined curves andoptically moved between the WIDE and the TELE, thereby carrying out thezooming operation.

An operation of the optical WIDE →the optical TELE →the collapsing mode,is carried out by rotating the cam ring 4 in the opposite direction bybeing driven by the gear unit 10 in a direction opposite to theabove-mentioned operation. Since the cam ring 4 is driven by the gearunit 10 as mentioned above, the collapsible lens 1 carries out thecollapsing operation and the zooming operation. On the other hand, bythe driving source such as the stepping motor 15 different from theabove-mentioned driving source, the third group is slightly displaced inthe optical axis direction. Accordingly, the focusing operation iscarried out (refer to an arrow G of FIGS. 2A, 2B and 2C).

A first embodiment of the lens driving mechanism according to thepresent invention will be described below. FIG. 4 is a partiallysectional view explaining the first embodiment. The lens drivingmechanism according to this embodiment is characterized in that an idlerotation section 15 c of a nut 16 is provided at only one of the ends ofthe lead screw 15 a serving as the output axis.

The nut 16 is screwed to a threaded portion 15 b of the lead screw 15 a,and the nut 16 is allowed to be advanced or retreated in the opticalaxis direction by the rotation of the lead screw 15 a, in which thestepping motor 15 serves as the driving source. An arm 17 placed next tothe nut 16 is provided by extending the third group frame 7 that servesas the lens holder. Next, when the nut 16 is moved towards the rightdirection of FIG. 4, the arm 17 moves the third group frame 7 towardsthe right direction of FIG. 4 against force of a spring 9 that is placedaround a guiding axis 14.

In addition, there is no lubricious grease in a bearing section betweenthe third group frame 7 and the guiding axis 14. Accordingly, since thespring 9 is placed around the guiding axis 14, the dispersion of thegrease caused by the expansion and contraction of the spring 9 is notoccurred.

Further, the arm 17 is not connected to the nut 16. When the nut 16 ismoved toward the left direction in FIG. 4, the force of the spring 9against the bearing section 7 b of the third group frame 7 forces thearm 17 towards the side of the nut 16, thereby moves the third groupframe 7 toward the left direction of FIG. 4.

In the present embodiment, the idle rotation section 15 c is placed ononly the imaging device side (the right side of FIG. 4) at the ends ofthe lead screw 15 a. The idle rotation section 15 c is the portion wherethe threaded portion 15 b is not placed, and the screw thread of the nut16 is not engaged. Thus, if the nut 16 moves to the right direction ofFIG. 4 and exceeds the threaded portion 15 b of the lead screw 15 a,this results in the situation that at the idle rotation section 15 c,only the lead screw 15 a is idly rotated, which is possible to preventthe further movement of the nut 16 and accordingly prevent the movementsof the arm 17 and the third group frame 7.

On the other hand, if the rotation of the lead screw 15 a is stopped,the nut 16 is urged towards the left direction of FIG. 4 by the spring9. Thus, by rotating the lead screw 15 a in the direction opposite tothe above-mentioned case, this results in the situation that the screwthread of the nut 16 is engaged with the screw thread 15 b of the leadscrew 15 a. Hence, it becomes possible to return to the movement towardsthe left direction of FIG. 4 in association with the rotation of thelead screw 15 a.

For example, if an initial position adjustment (a focus reset or thelike) of a lens L is carried out, a controller (not shown) controls therotation of the lead screw 15 a so that the nut 16 always reaches theidle rotation section 15 c. After the nut 16 reaches the idle rotationsection 15 c, the lead screw 15 a is reversely rotated. Thus, the nut 16is engaged with a starting edge of the screw thread 15 b.

Accordingly, it becomes possible to accurately adjust the initialposition of the lens L. In addition, if the lens L is a focus lens, itis possible to prevent biting of the screw thread of the nut 16 eventhough a trouble such as a focus error and the like occurs, if thecontroller to control the rotation of the lead screw 15 a so that thenut 16 always reaches the idle rotation section 15 c.

In the above-mentioned first embodiment, it is enough to place the idlerotation section 15 c on only one side of the ends of the lead screw 15a. Thus, as compared with the mechanism in the related art in which theidle rotation sections are placed on both ends of the lead screw 15 a,the length of the lead screw 15 a maybe shortened, which allow theentire lens barrel to be thinner.

Further, the idle rotation section 15 c is placed at the end of theimaging device side (the right side of FIG. 4) in the lead screw 15 a,and the arm 17 and the spring 9 are placed on the photographing deviceside with respect to the nut 16. Accordingly, even if the nut 16 is notmoved since the power source to the stepping motor 15 is turned off whenthe lens L is collapsed (refer to FIGS. 1A, 2A), the third group frame 7is allow to be pushed into the imaging device side, thereby attainingthe thinner size at the time of storage space of the lens L.

A second embodiment of the lens driving mechanism according to thepresent invention will be described below. FIG. 5 is a partiallysectional view explaining the second embodiment. The lens drivingmechanism according to this embodiment is characterized in that an idlerotation section 15 c of a nut 16 is placed at only one of the ends of alead screw 15 a that serves as the output axis and also characterized inthat a spring 9 serving as the forcing element is placed around a leadscrew 15 a. The latter characteristics are distinct feature from thefirst embodiment.

In the present embodiment, similar to the first embodiment, a nut 16 isscrewed to a threaded portion 15 b of the lead screw 15 a, and the nut16 is allow to be advanced or retreated in the optical axis direction bythe rotation of the lead screw 15 a, in which the stepping motor 15serves as the driving source. The arm 17 placed next to this nut 16 isplaced extendedly from the third group frame 7 serving as the lensholder. Then, when the nut 16 is moved towards the right direction ofFIG. 5, the arm 17 moves the third group frame 7 in the right directionof FIG. 5 by prevailing against the force of the spring 9.

Further, the arm 17 is not connected to the nut 16. When the nut 16 ismoved in the left direction of FIG. 5, the pushing force of the spring 9placed around the lead screw 15 a pushes the arm 17 towards the side ofthe nut 16, thereby moving the third group frame 7 to the left directionof FIG. 5.

In this embodiment, similarly to the first embodiment, the idle rotationsection 15 c is placed on only the imaging device side (the right sideof FIG. 5) of both ends of the lead screw 15 a. Thus, if the nut 16moves towards the right direction of FIG. 5 and exceeds the threadedportion 15 b of the lead screw 15 a, this results in the situation thatat the idle rotation section 15 c, only the lead screw 15 a is idlyrotated, which allows to prevent the further movement of the nut 16 andallows to accordingly prevent the movements of the arm 17 and the thirdgroup frame 7.

On the other hand, if the rotation of the lead screw 15 a is stopped,the nut 16 is pushed in the left direction of FIG. 5 by the spring 9.Thus, by rotating the lead screw 15 a in the direction opposite to theabove-mentioned case, this results in the situation that the screwthread of the nut 16 is engaged with the screw thread 15 b of the leadscrew 15 a. Hence, it becomes possible to return to the movement towardsthe left direction of FIG. 5 in association with the rotation of thelead screw 15 a.

As mentioned above, it is enough to place the idle rotation section 15 con one side of the ends of the lead screw 15 a. Thus, as compared withthe conventional mechanism in which the idle rotation sections areplaced on both ends of the lead screw 15 a, the length of the lead screw15 a may be shortened, which allows the entire lens barrel to bethinner. Further, in the second embodiment, the spring 9 is placedaround the lead screw 15 a. Thus, a direction of the force to be appliedfrom the nut 16 to the arm 17 and a direction of force with the spring 9allow to be adjusted coaxially, which enables the arm 17 to move forwardand backward smoothly.

A third embodiment of the lens driving mechanism according to thepresent invention will be described below. FIG. 6 is a partiallysectional view explaining the third embodiment. The lens drivingmechanism according to this embodiment is characterized in that the idlerotation section 15 c of the nut 16 is placed on only the subject side(the left side of FIG. 6) of both ends of the lead screw 15 a serving asthe output axis.

Because of such arrangement of the idle rotation section 15 c,positional relation between the nut 16 screwed to the threaded portion15 b of the lead screw 15 a and the arm 17 extended from the third groupframe 7 is opposite to the first embodiment.

Thus, in this embodiment, if the nut 16 moves towards the left directionof FIG. 6 and exceeds the threaded portion 15 b of the lead screw 15 a,this results in the situation that at the idle rotation section 15 c,only the lead screw 15 a is idly rotated, which is possible to preventthe further movement of the nut 16 and can accordingly prevent themovements of the arm 17 and the third group frame 7.

On the other hand, if the rotation of the lead screw 15 a is stopped,the nut 16 is pushed towards the right direction of FIG. 6 by the forceof the spring 9 against the bearing section 7 b of the third group frame7. Thus, by rotating the lead screw 15 a in the direction opposite tothe above-mentioned case, this results in the situation that the screwthread of the nut 16 is engaged with the screw thread 15 b of the leadscrew 15 a. Hence, it becomes possible to return to the movement to theright direction of FIG. 6 in association with the rotation of the leadscrew 15 a.

In this embodiment, for example, if the initial position adjustment (thefocus reset and the like) of the lens L is carried out, the controller(not shown) controls the rotation of the lead screw 15 a so that the nut16 always moves towards the left direction of FIG. 6. After the nut 16reaches the idle rotation section 15 c, the lead screw 15 a is reverselyrotated. Thus, the nut 16 is engaged with starting edge of the screwthread 15 b.

Accordingly, it becomes possible to accurately adjust the initialposition of the lens L. In addition, when the lens L is the focus lens,though the trouble such as the focus error and the like is induced, ifthe controller controls the rotation of the lead screw 15 a so that thenut 16 always reaches the idle rotation section 15 c, it is possible tosurely protect the chamfering of the screw thread of the nut 16.

In such a third embodiment, similarly to the first embodiment, the idlerotation section 15 c is placed on only one side of the ends of the leadscrew 15 a. Thus, as compared with the conventional mechanism in whichthe idle rotation sections are placed on both ends of the lead screw 15a, the length of the lead screw 15 a is allowed to be shortened, whichallows to make the entire lens barrel thinner.

Further, there is no lubricious grease in the bearing section betweenthe third group frame 7 and the guiding axis 14. Thus, even if thespring 9 is placed around the guiding axis 14, the dispersion of thegrease caused by the expansion and contraction of the spring is notinduced.

Moreover, placing the idly rotating section 15 c, on only the objectside of both ends of the lead screw 15 a, allows movement of the lens Lto the object side to be easily and accurately controlled. In short, Onthe side of the near focus of the lens L, the movement distance of thelens L is longer than that on the side of a far focus for the samedistance to the object. Accordingly, since the idle rotation section 15c is located on the side of the near focus of the lens L, the threadedportion 15 b of the lead screw 15 a can be used to the end. Further,since the initial position adjustment of the lens L can be carried outon the side of the near focus, it is possible to carry out the positioncontrol at the high precision.

A fourth embodiment of the lens driving mechanism according to thepresent invention will be described below. FIG. 7 is a partiallysectional view explaining the fourth embodiment. The lens drivingmechanism according to this embodiment is similar to the thirdembodiment, in that the idle rotation section 15 c of the nut 16 isplaced on only the object side (the left side of FIG. 7) of both ends ofthe output axis, the lead screw 15 a. However, it is different in thatthe spring 9 serving as forcing element is placed around the lead screw15 a.

Due to such arrangement of the idle rotation section 15 c, if the nut 16moves towards the left direction of FIG. 7 and exceeds the threadedportion 15 b of the lead screw 15 a, this results in the situation thatat the idle rotation section 15 c, only the lead screw 15 a is idlyrotated, which allows to prevent the further movement of the nut 16 andcan consequently prevent the movements of the arm 17 and the third groupframe 7.

On the other hand, if the rotation of the lead screw 15 a is stopped,the nut 16 is pushed towards the right direction of FIG. 7 by the spring9. Thus, by rotating the lead screw 15 a in the direction opposite tothe above-mentioned case, this results in the situation that the screwthread of the nut 16 is engaged with the screw thread 15 b of the leadscrew 15 a. Hence, it becomes possible to return to the movement towardsthe right direction of FIG. 7 in association with the rotation of thelead screw 15 a.

In this embodiment, for example, if the initial position adjustment (thefocus reset and the like) of the lens L is carried out, the controller(not shown) controls the rotation of the lead screw 15 a so that the nut16 always moves towards the left direction of FIG. 7. After the nut 16reaches the idle rotation section 15 c, the lead screw 15 a is reverselyrotated. Thus, the nut 16 is engaged with the beginning of the screwthread 15 b.

Accordingly, it becomes possible to accurately adjust the initialposition of the lens L. In addition, when the lens L is the focus lens,though the trouble such as the focus error and the like is induced, ifthe controller controls the rotation of the lead screw 15 a so that thenut 16 always reaches the idle rotation section 15 c, it becomespossible to surely prevent biting of the screw thread of the nut 16.

In such a fourth embodiment, similarly to the first embodiment, the idlerotation section 15 c is placed on only one side of the ends of the leadscrew 15 a. Thus, as compared with the conventional mechanism in whichthe idle rotation sections are placed on both ends of the lead screw 15a, the length of the lead screw 15 a is allowed to be shortened, whichallow to make the entire lens barrel thinner.

Further, placing the idle rotation section 15 c on only the object sideof the ends of the lead screw 15 a, allows movement of the lens L to theobject side to be easily and accurately controlled. In short, On theside of the near focus of the lens L, the movement distance of the lensL is longer than that of the side of the far focus for the same distanceto the object. Accordingly, since the idle rotation section 15 c isplaced on the side of the near focus of the lens L, the threaded portion15 b of the lead screw 15 a can be used to the end. Further, since theinitial position adjustment of the lens L can be carried out on the sideof the near focus, it is possible to carry out the position control atthe high precision.

Further, since the spring 9 is placed around the lead screw 15 a, thedirection of the force to be applied from the nut 16 to the arm 17 and adirection of force with the spring 9 are possible to be adjustedcoaxially. Thus, there is a merit that the advancing and retreatingmovement of the arm 17 is possible to be smoothly performed.

The above-mentioned respective embodiments have been described by mainlyexemplifying the application to the collapsible lens. However, theapplication range of the present invention is not limited to theabove-mentioned collapsible lens. That is, as the configuration of thedriving mechanism that allows to be miniaturized and to prevent bitingof the nut, it can be widely applied to a fixed barrel (a so-calledinner focus lens).

As mentioned above, according to the present invention, it has thefollowing effects. That is, an idle rotation section of a nut and theforcing elements are placed on only one side of the ends of an outputaxis. Then, if control becomes impossible, by always feeding the outputaxis in the direction of the idle rotation section, the re-initializingoperation is carried out to previously prevent biting between the outputaxis and the nut. Accordingly, it is possible to remove the idlerotation section and the pusher on the other side, and possible toshorten the output axis, shorten the guiding axis, and shorten a guidingaxis presser. Thus, it is possible to miniaturize a lens barrel, andmake a storage space of a collapsible lens thin, and further miniaturizethe image capture apparatus in which they are mounted.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A lens driving mechanism, comprising: a lens holder that holds a lensand has a bearing section for receiving an axis for guiding the lens tomove in an optical axis direction; driving means that has an outputaxis, in which a screw section to which a nut is screwed is formed, anda driving source for rotating the output axis; an arm that is providedby extending the lens holder, in such a way that a tip being locatednext to the nut of the driving means, and moves the lens holder withmovement of the nut; forcing means for forcing the tip of the arm in adirection to the nut; and an idle rotation section that is placed on oneside, on which the arm is placed for the nut, at an end of the outputaxis of the driving means, and has an axis diameter which disables thenut to be screwed, wherein the forcing means contacts a photographingdevice side of the bearing section.